Doctoral Degrees (Agricultural Economics)

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Browsing Doctoral Degrees (Agricultural Economics) by Advisor "Grové, Bennie"

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    An economic analysis of salinity management with evolutionary algorithms in Vaalharts
    (University of the Free State, 2017-01) Haile, Berhane Okubay; Grové, Bennie; Barnard, Johan; Matthews, Nicolette
    The main objective of this research was to develop a bio-economic salinity management model to evaluate the stochastic efficiency, water-use efficiencies and environmental impact of optimal irrigation-scheduling practices while taking cognisance of irrigation-water quality, soil conditions, irrigation-technology constraints, crops and stochastic weather. A bio-economic salinity management simulation model was developed in MATLAB through the integration of the Soil WAter Management Program (SWAMP), by combining electricity-cost calculations with enterprise budgets to evaluate the impact of current irrigation schedules used by irrigators. The resulting SWAMP-ECON model was linked to an evolutionary algorithm to determine the benefits of following an optimised irrigation-scheduling strategy for each field crop. The model was also extended to model inter-seasonal allocation of water between two consecutive crops grown on the same field, to evaluate changes in the irrigation schedule of the first crop to manage the impact of soil salinity on the second crop. Risk was included in the analyses through the use of a state-general characterisation, where decisions are made without any knowledge of which state will occur. The models were applied to a case study farm in Vaalharts Irrigation Scheme with a 30.1 ha centre-pivot irrigation-system. The farm is characterised by Bainsvlei soil type and a shallow water table close to or below the root zone. The scenarios considered to run the model were two water qualities (low and high), two irrigation-system delivery capacities (10 mm day-1 and 12 mm day-1), and three field crops (maize, wheat, and peas) with different salinity-tolerance levels. The field crops constitute the crops grown for intra-seasonal and one-year inter-seasonal applications. Stochastic efficiency, low water-use efficiencies and environmental-impact indicators were calculated to interpret results of irrigation-management options for achieving economic and environmental sustainability. The results show that the farmer's existing irrigation schedules for the field crops in the study were over-irrigation strategies characterised by low water-use efficiencies, which are the direct result of farmers ignoring the contribution of the shallow water table to crop water-use. Over-irrigation resulted in large amounts of drainage water releasing between 11 000 and 26 600 kg ha-1 of salt into the environment. Decreasing water quality increases the risk of failing to reach potential production levels of the more salt-sensitive crops (maize and peas), however, the impact on expected margin above specified costs was low. Peas is the most profitable enterprise, followed by maize, and then wheat. On average, the expected margin above specified costs for peas, maize, and wheat, respectively, is ZAR 448 370, ZAR 321 909 and ZAR 245 885. The conclusion is that the current irrigation strategy is inefficient, has a large impact on the environment and presents the opportunity to improve profitability through better irrigation-scheduling practices that acknowledge the contribution of the shallow water table. Results of the optimised irrigation schedules show significant increases in expected margin above specified costs, associated risk exposure, water-use efficiencies and water productivity, as well as decreases in environmental impact due to a reduction in the amount of salt leached (SL). The main contributing factor to the results is the fact that the amount of irrigation water could be reduced because the shallow water table contributed 40% to 62% to crop water-use evapotranspiration, depending on crop type, water quality, and irrigation-system delivery capacity scenario selected. The largest benefits were observed for the highly salt-tolerant crop (wheat), because no leaching was necessary to manage salt levels. Consequently, a large salt build-up in the soil was observed. Decreasing water quality, compared to good quality water, impacted more negatively on MAS, risk exposure and the extent of drainage losses by the more salt-sensitive crops. Irrigation-system delivery capacity did not affect water-application rates significantly, but the results show that it is easier to manage electricity costs with the larger capacity by using a time-of-use electricity tariff. The conclusion is that the benefit of an optimised irrigation strategy is considerable, though careful consideration should be given to the trade-off between decreasing water applications and increasing salinity levels in the soil. Results of the inter-seasonal optimised irrigation-scheduling strategy water-use show that the leaching needs to increase during the production of the first crop to reduce the starting soil-salinity level when the follow-up crop is planted, especially when the second crop is sensitive to high salinity levels. Low WUE, WP and profitability are the consequences, taking the follow-up crop into account. In conclusion, a risk-neutral farmer should only consider increasing the water applied to the first crop (e.g. maize) if the plan is to plant a salt-sensitive crop (e.g. peas) in the second season. In both the intra-seasonal and the inter-seasonal applications, a risk-averse decision-maker will use more irrigation water to reduce the variability of outcome. The main recommendation from this research is that alternative institutional arrangements should be considered to ensure that irrigators do not lose their water-use entitlements if the water that is not used is deemed a non-productive use. A scheme-level hydrology analysis is necessary to determine the impact on the water table if all water-users start mining the water table. Future research should focus on extending the model to include the long-term problem of salinity and enhancing the model to deal with state-specific applications of water to crops as new information becomes available to farmers about a state of nature.
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    ItemOpen Access
    Technical efficiency and risk preferences of cropping systems in Kebbi State, Nigeria
    (University of the Free State, 2013) Jirgi, Abigail John; Viljoen, M. F.; Grové, Bennie; Jordaan, Henry; Nmadu, J. N.
    The research investigated the risk attitude, risk sources and management strategies, and the technical and cost efficiencies of farmers in Kebbi State, Nigeria, with the aim of generating reliable information on the influence of risk attitudes of the decision-making behaviour of farmers and determinants of efficiency. Various techniques were applied in order to achieve the objectives of the study. They include: the Experimental Gambling Approach, Factor Analysis, Logit regression, Data Envelopment Analysis, Double Bootstrapping procedure and the Metatechnology Approach. Data to conduct the research was obtained mainly from primary sources through a questionnaire survey of 256 farmers, comprising 98 monocroppers and 158 intercroppers. Some of the important findings from the research are: · All the farmers exhibit some level of risk aversion. The intercroppers were statistically significantly more risk-averse than the monocroppers. Risk attitude influences the decisions farmers make in the production process and should be considered when formulating agricultural policies. · The most important sources of risk for both monocroppers and intercroppers are diseases, erratic rainfall, changes in government policy, changes in climatic conditions, price fluctuation (of inputs and outputs) and floods/storms. The most important risk management strategies for monocroppers are spraying for diseases and pests, spreading sales, borrowing (cash or grains) and fadama cultivation. These factors should be considered when designing extension programmes and insurance schemes. The intercrop farmers perceived family members working off-farm, spreading sales, intercropping and borrowing (cash or grains) as the most important coping strategies. · The main findings from the factor analysis for the sources of risk for the monocroppers and intercroppers are that the factors “social”, “rainfall” and “uncertainties” are important to both groups of farmers. Since farmers do not have control over the rainfall factor as a source of risk, there is, inter alia, a need to have an effective agricultural insurance scheme for the farmers in the study area. Farming experience, asset value, risk aversion and land degradation were found to have statistical significant influences on the choice of cropping systems in Kebbi State. · The results from the technical efficiency analysis suggest that there is scope for increasing the technical efficiency levels of both monocrop and intercrop farmers and hence their ability to increase output levels at current input levels and within the existing technology set. · Based on the metatechnology ratio, the millet/cowpea group were the more technically efficient, followed by the sorghum/cowpea group. The sorghum group were less technically efficient. This suggests that crop diversification, in order to manage risk sources, has the potential for improving crop productivity in Kebbi State. Crop combinations, however, prove to play an important role. Care should be taken to select the optimal combination of crops to include in the intercropping system. · In terms of cost efficiency, farmers in the study area were relatively cost-inefficient. The metatechnology ratio for cost efficiency depicts that the sorghum/cowpea group were more cost efficient than their counterpart sorghum, and millet/cowpea group. Selection of farm inputs at minimum cost will help to reduce production cost and hence improve profitability of the farmers. · Low levels of technical and cost efficiency suggest that major scope exists to increase performance of the farmers, even at their current output levels and within their existing technology set. Support services, such as subsidies on farm inputs, provision of credit and extension services of the new Agricultural Transformation Agenda Programme (ATAP), should be properly implemented and targeted at the small-scale farmers. · The determinants of efficiency differ between the monocroppers and intercroppers, and also differ between the intercrop groups. This suggests that different groups of farmers operate under different technology sets. · The results also suggest that the existing knowledge on the various factors that influence both technical and cost efficiency is not exhaustive and accordingly that there is a need to explore other characteristics that influence the farmers’ decision process within their technology set.